Thermally-controlled electric switch



R. L. FEARN, IR. THERMALLY CONTHOLLED ELECTRIC SWITCH.

APPLICATION FILED FEB. I2, 1920.

Patentedmay 31, 1921.A

4 SHEETS-SHEET I- SH01/Mug R. L. FEARN, 1R.

THERMALLY CONTROLLED ELECTRIC SWITCH.

APPLICATION FILED FEB. I2, 1920.

1,380,049. Patented May 31, 1921.

4 SHEETS-SHEET 2.

@lt/imm m R. L. FEARN, JII.

THEHNIALLY CONTROLLED ELECTRIC SWITCH.

APPLICATION FILED FEB. I2l 1920.

1,380,049. y PaIenIeaMay 31,1921,

4 SHEETS-SHEET 3.

l] nuewto z "UAM- R. l.. FEARN,1II. THERMALLY CONROLLED ELECTRIC SWITCH. APPLICATION FILED FEB. I2. 1920.

`4 SHEETS-SHEET 4.

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UNITED sTArEs-PATENr erica.

RICHARD L. FEARN, JR., OF WASHINGTON, DISTRICT 0F COLUMBIA, `A SSIGfNOIt l10 NATIONAL ELECTRICAL SUPPLY COMPANY, 0F WASHINGTON, DISTRICT OF COLUMBIA, A. CORPORATION OF VIRGINIA i 'rHEnMALLY-CONTROLLED ELECTRIC SWITCH; i

Speeication'of Letters Patent. Patented 31, 1921. i

Application filed February 12, 41920. Serial No. 358,251.

To allfwhom t may concern:

Be it known thatl I, RICHARD L. FEARN, Jr., a citizen ofthe United States, residing at' Washington, in the District of Columbia, havel invented certain new and useful Improvements in Thermally-Controlled Electrical Switches, of which the following 'is a specification.

This invention relates t0 thermallyl controlled electrical switches, and it comprises a contact member, releasable means for maintaining the contactl member in a fixed Y vmember 4from its first positionto its second position, all as more fully hereinafter set forth and as claimed. Y

At the present time, there are a number of thermally controlled electrical switches in use wherein a circuit is broken by the melting or fusing of an alloy. when a predetermined temperature is reached. These devices are applicablelfor use as fire alarms and other types of signals wherein the melt- 'ing or fusing o'f the alloy breaks a circuit or establishes one through a signal element, or wherein the fusible element separates or closes two contact members which are spring ressed toward or away from each other and which closeor open al circuit when the fusible element melts. These devicesarenot applicable to a temperature regulator where- ,in the amount of current supplied orthe amount of resistance 1n circuit may be ,varied vwhen a predetermmed temperature -ls reached. l

In the present invention I have devised a switch which may be set to furnish a maximum amount of current, ora maximum uantity of heat, referred to hereinafter as high heat having means for automatically cutting oI' theI portion of the current supplied (or a. portion of theheat furnished) when a 'certaintemperature is reached thus throwing the'device into low heat. The device is capable of manual 'operation and vmay be shifted from high heatto low `heat at any'tme. 1 The contact member, which isj thrown from one position to another when the switch vis .the circuitL employed ,with this type... of

is arranged a rotatingdisk'or plate 4 (se'e changed from high heat'to low heat, is held 51 in high heat position by suitable mechanism against the action of a spring. When a pre,- determined temperaturevis reached the fusible substance melts releasing the, mechanism holding the contact member and pere0 mitting it to move to low heat position.

a rotary switch showing the contact member in high heat position to the left of the center.

Fig. 2 is a similar view showing the contact member in high heat position tothe right of the center.

Fig. 3 1s a transverse sectional view of the switch shown in Figs. 1 and 2.

Fig. iis a plan viewof the inner face of the coverof the casing in which the alloy v1s placed.

Y Fig. 5 is a perspective view of a rotating disk which is arranged in the casing and surrounded by the alloy. y

Fig. 6 is a dia rammatic illustration of 80 the circuit used w1th this t pe of switch.

Fig. 7 is a plan view, o anothertype of lswitch having a pivoted contact member.

Fig.- 8 'is a sectional view on the line 8--8 of Fig. 7. 85

Fig. 9 isa detailed perspective view of the operating lever. f f- Fig. 10 is a detail perspective view of the 'bearing member.

Y, Fig. 111s a detailed perspective view of 90 the ivotedv contact member.

Fig. 1 2 is a sectional view similar to Fig. 8 showing the switch in low heat position. 'Fig 13 is atransverse sectionalview at right angles to Fig. 12. f t

Fig. 14-is a detailed perspective view of one ofthe contacts carried by the switch and Fig. 15 is a diagrammaticillustration of switch.

Referring to Figs. 1 to 6 of, the drawings, in the form shown thereinthe switch comprises a base 1 of insulating material in which is mounted a metallic casing 2' having a cover or closure 3. Within the casing there Fig. 5) provided with openings 5. The cover 1s provided with projections 6 ar- `f ranged eccentrically of these openings. The casing is filled with a substance, preferably metal;` 7 adapted to melt or fuse at a predetermined temperature. The alloy entirely surrounds the rotating plate as shown. The shaft 8 projects from the rotating disk and extends through the cover. As shown this shaft is provided with asquared end 9. Mounted on the face of the switch are a. plurality of contacts 10, 11, 12 and 13. These contacts are adapted to be connected to the source of current in a manner to be described and are connected to each other by a movable Contact member generally designated by the reference numeral 14.

` As shown the movable contact member' consists of a plate 15 rotatablymounted on the casing and secured vthereto by screw 16. 1t is spaced therefrom by a spacing plate 17. Suitably secured to plate 15 are a pair of contact strips 18 and 19 separated from the remainder of the contact element by insulation 20. A strip of insulation 20 is arranged beneath the contact strips. The

center of the plate is cut away as shown and is adapted to receive a trip member 21 carried on the square end ofthe shaft 8. This trip member is provided with a spring nger 22 engagin Ashoulders 23 and 24 of the contact plate. spring 25 issecured to the casing and to the contact plate,

the spring being adapted to move the plate from the center position shown in full lines in Fig. 1 to the dotted line position illustrated in Fig. 6.

rllhe connections andv arrangement of the electrical circuit for employing a switch of this character are shown in Fig. 6 of the drawings. In this figure, `a source of electric current is indicated by the letter A to which is connected a pair of conductors 26 and 27. rlhese conductors are connectedto the two contacts 13 and 10. Branch `wires 28 and 29 are connected to the conductors, and electrical heating elementsy 3() and 31'. are connected to these wires. The heating element 30 is connected to the contact member 11 by conductor 32 and the heating element 31 is connected to contact member 12 by conductor 33.- When the contact member is in the full line/position illustrated in Figs. 1, 2 and 6 of the drawing current passes through conductor 27, wire 29, heating unit 31,` conductor 33, contact 12, Contact strip 18 and contact 13 to the conductor 26. At the same time, current passes from the `conductor l27 through contact 10, contact .strip 19, Contact 11, conductor 32, heating unit 30, and wire28, thence to the conductor 26. The two heating units are thusin par allel taking a maximum kamount of current and giving a maximum amount of heat.`

When the switch is operated, ,to move the contact plate to either the dotted line position illustrated in Fig. 1, or the dotted line 'I of the drawings.

assente -contact 12, through the contact strip 18 or 19 to contact 11, thence through the heating unit 30 to conductor 26. Under such conditions the two heating units are arranged in series, andthe current `reduced thereby. furnishing a less amount of heat or low heat.v

ln the form illustrated in Figs. 7 to 14 of the drawings, the base 34 receives the supporting member 35 which is made preferably of insulating material. Arranged between the base and the supporting member are a pair of diaphragms 36 and 37. These Vdiaphragms are made of resilient or spring metal and are normally conveX upon their upper surfaces. The alloy 38 is arranged between the)diaphragms and a trip member 39 is securedto the upper face of the inner diaphragm. As shown, this member is provided with a beveled end 40. A pair of contacts 41 are suitably. arranged upon the supporting member. the"l contacts is sho-wnin detail in Fig. 14

secured to vthe supporting member by screws 42. A lever 43l is 'pivotedfin a bearing member 43 secured to the supporting member. rllhe construction of the bearing member is shown in detail in Fig. 10 of the drawings. rlFhis lever is provided with an arm 45 normally resting upon the beveled end 40 of the trip member. A spring 46 is secured upon a screw or bolt 47, carried by the supporting member. @ne end of the spring bears against the supporting member at 48 and the other end 49 bears against the arm 45. `A Contact strip 50 (see Fig. 11)` is pivoted to the bearing member 43.` rlhe bearing member is provided with a pair of ears 51, which 1 are -secured to the supporting strip by suitable fastening elements 52 passing through the supporting strip and through openings 53 formed fin' the ears. The body vof the bearing member is cut away as vat 54 to permit movement of the contact strip and the arms 55 and 56 of the contact strip are provided with openings 57 and 58 which are received on bearings 59 arranged on the bearing member. The operating 'lever is provided with an extension 60 the end of which is slotted at 61. The extension is further providedwith an opening 62 arranged in alinement with the slot. A pin 64 is arranged within the contact strip 50, the outer y end of the) pin passing through an opening rllhe contact members are 'lFhe construction of mounted on the pin.l rlhe end of the pin is forked and the forked ends'68 are received in the slot 61 and opening 62 of the operating r trated in Fig. of the drawings.-V

l operating lever is moved upon its pivot the spring 66 is compressed until; the inner end of pin 64 passes thel center line ,of the pivot. When the lever is moved farther, the contact strip is thrown from the position illustrated in Fig. 12 of lthe drawings, lto the position illustrated in Fig. 8,. closing the' circuit between the two contacts 41.

The electric circuit used in connection with this type of switch is diagrammaticall illusn this current to which are connected conductors 69 and 70. These conductor members are connected to the opposite ends of a heating unit 71. When the current passes from the source of current A through conductor 69, heating unit 71, and 'through conductor 70 to the source of current, the maximum resistence is in circuit reducingr the'current,

giving low heat. The contact strip 50 is then in the position shown in Fig. 12 of the drawings, the arm vhaving been released romthe trip member 39. The contact members 41 are diagrammatically illustrated in Fig. 15 and the movable contact 50 is diagrammatically illustrated as a switch arm..-

Contacts 41 are connected to the conductor 70 and to a point between the two ends of the electrical heating unit 71 by conductors 72 and 73 respectively. When the contact ,strip is in the full line position illustrated in this view corresponding -with Fig. 8 or,

the. drawings, a portion of the heating unit is cut out, thus increasing the current in the heating unit andincreasing the degree of heat.

- The operation of the form shown in Figs. 1 to 6 of the drawings is as follows:

When the switch is inthe position illustrated in Fig. 1 of the drawings, spring 25 tends to movethe contact plate 14 and its associated parts to the position shown in dotted lines in Fig; 6 of the drawings. r1`his is prevented by the engagement of shoulder 24 and finger 22. Whenthe degree of heat reaches the predetermined point and alloy 7 is melted, the contact plate 14 and the rotating disk are moved to the dotted line position shown in Fig. 6 bythe action of spring 25. This movement breaks the connection between the contacts 10 andl 11 and between lthe contacts 12 and 13and establishes .con-

nection between contacts 11' and 12 by conv tact strip 18. The heating units 30 and 31 .plate is freely movable on its /pivot 16, indeee of heat.

pressure exerted upon the spring nger 22 due to its engagement with shoulders 24. This rotates the disk 4 which-is freely rotatable when the alloy is melted.

When the switch is again set forv high heat, the spring finger 22 bears against shoulders 23 as shown in Fig; 2 of the drawings overcoming the pressure Jof? the springl 25 which tends to move the contact plate 14 to the dotted line position shown in Fig. 1. rlhe alloy 7 ,being solid until the predeter` mined temperature is reached, prevents rotation -of disk 4 and thus holds the parts in set position. However, when the alloy melts the resistance to the pressure of the spring 25 is .removed and the contact plate 15 is moved to the right or left, as the case may be, to break the connections between the pairsof contacts at each side andfestablish connection between the center contacts.

r1`he device is manually operable at all, times to change the switch from one posi tion to the other. A suitable handle 100 is "attached to the contact plate 15 and this pendently of the*i rotating disk. l/Vhen the switch is in the high heat position shown in Fig. 1l and it is to'be changed to low 'heat the plate 15 is rotated to thegdotted linepof sition. To return. to high heat the operation is reversed. l/V hen the switchis in the position shown in Fig. 2, it may be' readily changed to the low heat position shown in dotted lines in Fig. 6 by rotating the disk in the opposite direction and -may be readily returned to high heat position. 1n the form shown in Figs. 7 to 15er the drawings, spring 46 normally tends to force arm 45 downwardly to Ithe position illustrated in Fig. i' the drawings, to break the connection between the contacts 41, which short circuit part of the heating unit. rlhe diaphragme 36 and 37 are made of spring iot -material and are normally convex upon their At normal temperature, thealloy 38 is hard V115 and the pressure of vspring 46 is resisted. However, when the .predetermined temperature is reaohedand the alloy melts, the pressure causes the diaphragms. to give inwardly, permitting the trip member to move 120 suficiently to release arm 45. When this'- occurs, the contact member 50 is moved to the position illustrated in Fig. 12 of thev drawings, breaking the connection between the contacts 41 and throwing the entire re- 125 sistance unit 71 v.into circuit. When the entire resistance unit is in circuit the current ils decreased thus decreasing the degree of eat. i

This switch .is also manually operable toilo' permit change from high heat to low heat or vice versa at-any time. As shown, ythe trip member 39 is provided 4with a beveled end l0 which engages the beveled end of 4 arm 45 with sufiicient force to 'overcome the action of spring 46. However, if additional pressure is applied to lever 43, the arm will be moved past the trip member 39 and contact strip y50 moved from the position shown in Fig. 8 to the-position shown in lFig. 12, and it may be returned to high heat position by forcing the arm 45 past the trip member 39 and seating in on the beveled end 40. O

From the above description of the con` y struction and operation of these two forms connections to the electric circuit and heating units form no part of the linvention as sucli arrangements are optional and the same results can be obtained with many different constructions. The invention herein described consists of a thermally controlled .switch having a contact member adapted to assume either one of twc positions with releasable means for maintaining said contact member in one of said positions and means for moving said contact membery to the second position, together with thermallycontrolled means for controlling said releasable means, the switch being manually operable and being resettable.

lt is understoodthat the term alloy as used herein, is not limited to its ordinary meaning, buttincludes any composition or material, Vmetal or non-metal which is solid at normal temperatures `and has amelting point substantially the same as the degree of heat desired. Thus, the casing may be filled with paraiiin, waX or similar materials and a pure metal, such as lead, may be employed instead of an alloy.-

The .various uses to which the switch may be adapted are too numerous to mention but it-.is especially adapted for use in connection with electric heatingcdevices wherein an initial high heat is desired to raise the temperature of the material being heated, and a constant supply of heat of a lesser degree is desired to maintain the l material at the proper temperature during continued heating.

The device maybe employed as a temperature regulator in a room, the coils 30 and 31 or the coil 70 being used to heat the room, and the alloy or other substance being of a composition that will melt at the temperature at which the room is to be maintained. lff the room is cold the device is arranged for high heat and the vcoils are of suiiicient insane-e capacity to raise the Jiinperature in the room. When the desired temperature is reached, the alloymelts andthe device is thrown into low heat furnishing just suffi! cient heat to maintain `the temperature ,of

the room at the desired point. v

rllhe device may also be employed in connection with various types of electrical heating apparatus such as glue pots, domestic f lbe subjected to the same temperature as the device or object being heated, to properly function. u Y

Vf hat l claim is:

l. A resettable, thermally controlled switch comprising a base, a casing carried by the base, a fusible alloy arranged in said casing, said alloy being solid at normal tempeinture, a contact member arranged onsaid base, releasable `means for maintaining said contact member in vone position, and means for moving'said contact member to a second position, said releasable means being adapted to release said contact member when said alloy ifuses. p .f

2. A resettable, thermally controlled switch comprising a base, a casing carried by the base, a fusible alloy arranged in said casing,

said alloy being lsolid at normal temperature,

a contact member arranged on said base, releasable means for maintaining said Contact member in fone position, means for moving said contact member to a second position, I

said releasable means being adapted to release said contact member when said alloy,

fuses, and .manually operated means for moving said contact member from-its first position to its second position. y

3. A resettable, thermally controlled switch comprising a base, a casing carried by 'the base, a fusible alloy arranged in said casing,

said alloy being solid at normal temperature, a contact, member arranged on said base, releasable means for maintaining said contact member in one position, and a spring for moving said contactmember to ahsecond position, said releasable` means beingiadapted tov release said contact member. l f 4. A resettable, thermally controlled switc comprisin a base', a casingcarried by the base, a fusible alloy varranged insaid casing,

said alloy being solid at normal temperature,

a contact member arranged on saidbase, a tripmember mounted on said casing and adapted to engage said contact .member to lll@ maintain it in one position, and means for moving said Contact member to a second position, said means being adapted to release said Contact member.

5. A thermally controlled swith Comprising a base, a easing carried by the base,

a rotatable member arranged Within the Casing, an alloy arranged in the easing and entirely surrounding said member, said alloy being solid at normal temperature, a shaft projecting from said' rotatable member and extending through the easing, a plurality of contacts arranged on the face of the casing, a rotatable Contact member arranged on said easing, Contact strips Carried by said Contact member and adapted to connect said contacts, a spring secured to the casing and to said rotatable Contact member, and a trip member arranged on the end of said shaft and engaging said movable Contact member to prevent rotation When said alloy is solid.

6. A thermally Controlled switch com prising a base, a casing carried by the base,

a rotatable disk arranged Within the casing, an allo-y arranged in the casing and entirely surrounding said disk, said alloy being solid at normal temperature, a shaft projecting from said rotating disk and extending through the easing, a plurality of contacts arranged on the face of the Casing, a rotatable Contact member secured to the face of the easing, Contact strips Carried by said rotatable Contact member and adapted to Connect said contacts, a spring secured to the casing and to the Contact member, and a trip member arranged on the end of said shaft engaging said movable Contactv mem* ber to prevent its rotation when said alloy is solid. y

ln testimony whereof I affix my signature in the presence of tWo Witnesses.

CEAS. O. REED, W. M. JEWELL. 

